Abrading operations are performed on a workpiece, for example, to achieve a smoother, level surface on the workpiece, or to remove unwanted material, such as paint, which has adhered to the workpiece surface. A common abrading or sanding operation is performed on wood products, such as furniture, in order to produce a smooth surface in preparation for painting or for finishing the furniture.
When sanding a planar surface, it is particularly desirable that the surface be finished so that is it level, and so that the surface of the workpiece does not appear distorted or disfigured due to an uneven sanding operation.
Achieving a smooth and level sanded surface can be somewhat difficult. Namely, it is difficult to maintain a conventional sanding apparatus in a level plane, particularly when the workpiece surface is uneven. Thus, there may be a tendency for a conventional sanding apparatus to follow any imperfections in the surface and by doing so, to accentuate these imperfections even more. On a larger surface, such as the top of a table, these imperfections in the level of the surface caused by an uneven sanding operation may be quite noticeable.
Conventional apparatus have been disclosed for performing various abrading operations. In U.S. Pat. No. 785,024 by Shaver, a polishing machine is disclosed which includes a frame supported by a pair of wheels which has a rotary disc which depends downwardly from the frame at a location forward of the wheels. The polishing apparatus is manually manipulated by a handle attached to the frame.
An apparatus for cleaning a vertical wall is disclosed in U.S. Pat. No. 1,044,423 by Rosa, which includes a wheeled carriage assembly which is supported on a floor and which has an arm extending upward from the carriage to which is attached a vertical rotating cleaning disc.
U.S. Pat. No. 1,195,555 by Campbell discloses a floor grinding and polishing machine having a carriage frame supported on a pair of wheels, and a rotary disc supported for horizontal rotating movement which is mounted on the carriage frame forward of the wheels.
A grinding machine, disclosed by Mummert et al in U.S. Pat. No. 1,413,928, includes an upstanding carriage supported on four wheels. An elongated arm extends horizontally from a top portion of the carriage and has a vertically rotating grinding wheel at its distal end.
In U.S. Pat. No. 1,725,899 by Chase, there is disclosed a stone grinding machine including a wheeled carriage for supporting a movable elongated frame on a track, and a horizontal rotating disc depending downwardly from the distal end of the frame.
Toffolo, U.S. Pat. No. 1,832,267, discloses a rotary polishing machine which includes a motor supported by a two-wheeled carriage which is connected to a pair of horizontally rotating polishing stones by an elongated boom member.
A surface finishing machine is disclosed in U.S. Pat. No. 2,507,052 by Robinson, which includes a frame having four downwardly depending members for supporting the frame, and a rotating disc which depends from a drive motor attached to the frame.
In Elias, U.S. Pat. No. 4,241,471, there is disclosed a glass polishing apparatus which is adapted to be mounted to the windshield wipers of a motor vehicle.